Vol. XXXIV. March, 1916. No. 3 



BIOLOGICAL BULLETIN 



THE LOCOMOTIONS OF SURFACE-FEEDING CATER- 

 PILLARS ARE NOT TROPISMS. 



C. H. TURNER, 

 SUMNER HIGH SCHOOL, ST. Louis, Mo. 



PRELIMINARY OBSERVATIONS. 



While collecting cherries from a tree a large number of apple- 

 tent caterpillars were thrown upon the ground. Later several 

 of these were noticed climbing the trunk of the tree. They con- 

 tinued onward and upward ; some to the top of the tree and others 

 to certain branches. Near the tree was a rustic chair, the top 

 of the curved back of which was separated from the trunk by 

 about three inches. Several caterpillars climbed the back of 

 this chair. When they reached the top, they would elevate the 

 front portion of the body, wave it back and forth and around for 

 a few minutes and then proceed down the opposite side of the 

 curved arm. Sometimes the insect would turn about and 

 retrace its steps. These observations suggested two questions. 

 Are these caterpillars guided by a negative geotropism? If so, 

 why did those that had reached the top of the chair descend? 



TECHNIQUE. 



These experiments were performed upon a wooden vertical 

 maze (Figs. I. 2) and a copper horizontal one (Fig. 3); both of 

 the open type. The former was used in the field and the latter 

 in an out-door insectary. 



The vertical maze (Figs. I, 2) consists of a cylindrical post 

 about four feet tall and an inch and a half in diameter, to which 

 are attached five adjustable rectangular arms. Some of these 

 arms are straight and unjointed; others are formed of three 



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